Update on Calcitonin Gene-Related Peptide Antagonism in the Treatment of Migraine

Mode and site of action of therapies targeting CGRP signaling

Targeting CGRP has proved to be efficacious, tolerable, and safe to treat migraine; however, many patients with migraine do not benefit from drugs that antagonize the CGRPergic system. Therefore, this review focuses on summarizing the general pharmacology of the different types of treatments currently available, which target directly or indirectly the CGRP receptor or its ligand. Moreover, the latest evidence regarding the selectivity and site of action of CGRP small molecule antagonists (gepants) and monoclonal antibodies is critically discussed. Finally, the reasons behind non-responders to anti-CGRP drugs and rationale for combining and/or switching between these therapies are addressed.

The temporal trend of placebo response in migraine prevention from 1990 to 2021: a systematic literature review and meta-analysis with regression

BACKGROUND

Migraine affects 1.1 billion people globally and is the second leading cause of disability worldwide. In clinical trials, treatment efficacy is evaluated by comparing the differential responses in the treatment and placebo arms. Although placebo response in preventive migraine trials has been studied, there is limited research examining temporal trends. This study evaluates the trend of placebo response over thirty years in migraine prevention trials and investigates the association of potential confounders, such as patient, treatment, and study characteristics on placebo response using meta-analysis with regression.

METHODS

We conducted literature searches from January 1990 to August 2021 in bibliographical databases (PubMed, Cochrane Library, and EMBASE). Studies were selected according to PICOS criteria and included randomized, double-blind, placebo-controlled trials evaluating preventive migraine treatments in adult patients diagnosed with episodic or chronic migraine, with or without aura. The protocol was registered with PROSPERO (CRD42021271732). Migraine efficacy outcomes included were either continuous (e.g., monthly migraine days) or dichotomous (e.g., ≥ 50% responder rate (yes/no)). We assessed the correlation of the change in outcome from baseline in the placebo arm, with the year of publication. The relationship between placebo response and year of publication was also assessed after accounting to confounders.

RESULTS

A total of 907 studies were identified, and 83 were found eligible. For the continuous outcomes, the change from baseline in mean placebo response showed an increase over the years (rho = 0.32, p = 0.006). The multivariable regression analysis also showed an overall increase in placebo response over the years. The correlation analysis of dichotomous responses showed no significant linear trend between publication year and mean placebo response (rho = 0.08, p = 0.596). Placebo response also varied by route of administration.

CONCLUSION

Placebo response increased over the past 30 years in migraine preventive trials. This phenomenon should be considered when designing clinical trials and conducting meta-analyses.

Management of chronic migraine

Chronic migraine is a neurologic disorder associated with considerable disability, lost productivity, and a profound economic burden worldwide. The past five years have seen a dramatic expansion in new treatments for this often challenging condition, among them calcitonin gene related peptide antagonists and neuromodulatory devices. This review outlines the epidemiology of and diagnostic criteria and risk factors for chronic migraine. It discusses evidence based drug and non-drug treatments, their advantages and disadvantages, and the principles of patient centered care for adults with chronic migraine, with attention to differential diagnosis and comorbidities, clinical reasoning, initiation and monitoring, cost, and availability. It discusses the international guidelines on drug treatment for chronic migraine and evaluates non-drug treatments including behavioral and complementary therapies and lifestyle modifications. Finally, it discusses the management of chronic migraine in special populations, including pediatrics, pregnancy, and older people, and considers future questions and emerging research in the field.

Peptide ligand interaction with maltose-binding protein tagged to the calcitonin gene-related peptide receptor: The inhibitory role of receptor N-glycosylation

Calcitonin gene-related peptide (CGRP) and adrenomedullin (AM) are peptide hormones and their receptors play a critical role in migraine progression and blood pressure control, respectively. CGRP and AM receptors are structurally related since they are the complex of the calcitonin receptor-like receptor (CLR) with the different types of receptor activity-modifying protein (RAMP). Several crystal structures of the CGRP and AM receptor extracellular domain (ECD) used maltose-binding protein (MBP) as a tag protein to facilitate crystallization. Unexpectedly, the recent crystal structures of CGRP receptor ECD showed that the N-terminal tag MBP located in proximity of bound/mutated peptide ligands. This study provided evidence that MBP N-terminally tagged to the CGRP receptor ECD formed chemical interaction with the mutated peptide ligands. Interestingly, N-glycosylation of the CGRP receptor ECD was predicted to prevent MBP docking to the mutated peptide ligands. I found that the N-glycosylation of CLR ECD N123 was the most critical for inhibiting MBP interaction with the mutated peptide ligands. The MBP tag protein interaction was also dependent on the sequence of the peptide ligands. In contrast to the CGRP receptor, the MBP tag was not involved in peptide ligand binding at AM receptor ECD. Here, I provided evidence that N-glycosylation of the CGRP receptor ECD inhibited the tag protein interaction suggesting an additional function of N-glycosylation in the MBP-fused CGRP receptor ECD. This study reveals the importance of using tag protein-free versions of the CGRP receptor for the accurate assessment of peptide binding affinity.

Effect of Collaborative Care for Persistent Postconcussive Symptoms on Academic Function: A Randomized Clinical Trial

BACKGROUND

There is limited long-term data on the course of school-related problems and academic needs for youth with persistent post-concussive symptoms (PPCS).

METHODS

This was a randomized trial comparing collaborative care to usual care for 200 youth 11-18 years of age with PPCS. In this report, the main outcomes were academic functioning, GPA, school absences, date of return to school, and school days missed.

RESULTS

Youth were mean age of 14.7 (SD = 1.7), 62.0% female. New or worsening academic problems occurred in half of participants in both groups at 12 months after injury. Students were most concerned about grades and falling behind. There were no significant differences by study group on school problems or GPA, but number of days missed was lower in the collaborative care group compared at 3 months (12.5 [SD = 14.5] vs 16.1 days [20.4] adjusted relative risk [aRR] 0.67 [95% CI: 0.61, 0.74; p < .001]), 6 months (14.5 [22.1] vs 19.3 [26.6] aRR 0.77 [95% CI: 0.71, 0.84; p < .001]), and 12 months (16.9 [25.4] vs 19.6 [27.7], aRR 0.68 [95% CI: 0.62, 0.74; p < .001]).

CONCLUSIONS

Youth with PPCS are at high risk of school problems in the year after injury.

Calcitonin: current concepts and differential diagnosis

Calcitonin (CT) is most effectively produced by the parafollicular cells of the thyroid gland. It acts through the calcitonin receptor (CTR), a seven-transmembrane class II G-protein-coupled receptor linked to multiple signal transduction pathways with its main secretagogues being calcium and gastrin. It is clinically used mostly in the diagnosis and follow-up of medullary thyroid carcinoma (MTC). Hypercalcitoninemia can be attributed to primary (e.g. CT-secreting tumor) or secondary (e.g. due to hypercalcemia) overproduction, underexcretion (e.g. renal insufficiency), drug reaction (e.g. β-blockers), or false-positive results. In clinical practice, elevated basal calcitonin (bCT) is indicative, but not pathognomonic, of MTC. Current literature leans toward an age as well as gender-specific cutoff approach. bCT >100 pg/ml has up to 100% positive prognostic value (PPV) for MTC, whereas bCT between 8 and 100 pg/ml for adult males and 6 and 80 pg/ml for adult females should be possibly further investigated with stimulation calcitonin (sCT) tests. Calcium is showing similar efficacy with pentagastrin (Pg) sCT; however, the real value of these provocative tests has been disputed given the availability of new, highly sensitive CT immunoassays. Anyhow, evidence concludes that sCT <2 times bCT may not be suggestive of MTC, in which case, thyroid in addition to whole body workup based on clinical evaluation is further warranted. Moreover, measurement of basal and stimulated procalcitonin has been proposed as an emerging concept in this clinical scenario. Measuring bCT levels in patients with thyroid nodules as a screening tool for MTC remains another controversial topic. It has been well established, though, that bCT levels raise the sensitivity of FNAB (Fine Needle Aspiration Biopsy) and correlate with disease progression both pre- and postoperatively in this situation. There have been numerous reports about extrathyroidal neoplasms that express CT. Pancreatic, laryngeal, and lung neuroendocrine neoplasms (NENs) are most frequently associated with hypercalcitoninemia, but CT production has also been described in various other neoplasms such as duodenal, esophageal, cutaneous, and paranasal NENs as well as prostate, colon, breast, and lung non-NENs. This review outlines the current biosynthetic and physiology concepts about CT and presents up-to-date information regarding the differential diagnosis of its elevation in various clinical situations.

Headache and immunological/autoimmune disorders: a comprehensive review of available epidemiological evidence with insights on potential underlying mechanisms

Several lines of evidence support a role of the immune system in headache pathogenesis, with particular regard to migraine. Firstly, alterations in cytokine profile and in lymphocyte subsets have been reported in headache patients. Secondly, several genetic and environmental pathogenic factors seem to be frequently shared by headache and immunological/autoimmune diseases. Accordingly, immunological alterations in primary headaches, in particular in migraine, have been suggested to predispose some patients to the development of immunological and autoimmune diseases. On the other hand, pathogenic mechanisms underlying autoimmune disorders, in some cases, seem to favour the onset of headache. Therefore, an association between headache and immunological/autoimmune disorders has been thoroughly investigated in the last years. The knowledge of this possible association may have relevant implications in the clinical practice when deciding diagnostic and therapeutic approaches. The present review summarizes findings to date regarding the plausible relationship between headache and immunological/autoimmune disorders, starting from a description of immunological alteration of primary headaches, and moving onward to the evidence supporting a potential link between headache and each specific autoimmune/immunological disease.

CGRP Inhibitors and Oxidative Stress Biomarkers in Resistant Migraine: A Real-Life Study with Erenumab, Fremanezumab, and Galcanezumab

Patients with high-frequency resistant migraine and medication-overuse headache are still the main clinical challenge in tertiary headache centers. The approval of targeted antibodies against the calcitonin gene-related peptide (CGRP) and its receptor represents a powerful instrument. In this study, we observed how biological and clinical features of resistant migraineurs responded to erenumab, fremanezumab, or galcanezumab. We found a reduction in advanced oxidation protein products (AOPP) as a biomarker of improved redox state after six months of treatment. We also found that treatment efficacy was precocious and maintained with high individual responder rates. In particular, seven out of ten patients achieved a reduction of 50% from the baseline at three months, which was maintained at six months, while about one out of our patients experienced a 75% reduction in headache frequency from the first month of treatment. The migraine disability assessment (MIDAS) and the associated fatigue, anxiety, and sleep quality also significantly improved. The allodynia symptom dropped from moderate/severe to mild/absent as a sign of central sensitization reduction. Our study confirmed the safety and efficacy of CGRP inhibition in real-life, high-challenging patients. Additional evidence is needed to understand the role of oxidative stress as a migraine biomarker.

Could erectile dysfunction be a side effect of CGRP inhibition? A case report

Background

Recently, antimigraine drugs targeting the calcitonin gene-related peptide pathway have been approved for clinical use as preventive migraine medication.

Case report

We present a case of a 54-year-old male migraine patient, who reported erectile dysfunction as a possible side effect of treatment with galcanezumab, a monoclonal antibody targeting calcitonin gene-related peptide. His potency recovered after treatment discontinuation.

Discussion

As calcitonin gene-related peptide is involved in mammalian penile erection, erectile dysfunction is a conceivable side effect associated with calcitonin gene-related peptide inhibition. Postmarketing surveillance will elucidate the actual incidence of erectile dysfunction in patients using these new antimigraine drugs, and determine whether a causal relationship between calcitonin gene-related peptide inhibition and erectile dysfunction exists. This would be relevant not only because of the direct sexual consequences of erectile dysfunction, but also considering the potential cardiovascular consequences of calcitonin gene-related peptide (receptor) blockade and the association of both migraine and erectile dysfunction with cardiovascular disease.

Conclusion

Erectile dysfunction might be an overlooked, but reversible side effect in male migraine patients using monoclonal antibodies that inhibit the calcitonin gene-related peptide pathway, including galcanezumab. This paper may raise clinical awareness and suggest that this potential side effect needs to be studied further.

Investigating Migraine-Like Behavior using Light Aversion in Mice

Migraine is a complex neurological disorder characterized by headache and sensory abnormalities, such as hypersensitivity to light, observed as photophobia. Whilst it is impossible to confirm that a mouse is experiencing migraine, light aversion can be used as a behavioral surrogate for the migraine symptom of photophobia. To test for light aversion, we utilize the light/dark assay to measure the time mice freely choose to spend in either a light or dark environment. The assay has been refined by introducing two critical modifications: pre-exposures to the chamber prior to running the test procedure and adjustable chamber lighting, permitting the use of a range of light intensities from 55 lux to 27,000 lux. Because the choice to spend more time in the dark is also indicative of anxiety, we also utilize a light-independent anxiety test, the open field assay, to distinguish anxiety from light-aversive behavior. Here, we describe a modified test paradigm for the light/dark and open field assays. The application of these assays is described for intraperitoneal injection of calcitonin gene-related peptide (CGRP) in two mouse strains and for optogenetic brain stimulation studies.